When a curve of a road ahead of the vehicle is detected from map data, control can be exercised to provide driving assistance to pass through the curve, for instance, by automatically decelerating the vehicle before the curve and assisting a driver of the vehicle in manipulating a steering wheel in order to obtain an appropriate steering angle.
The shape of a road may be changed by road construction. Therefore, after the creation of map data, bypass road construction may be conducted to eliminate a curve or road improvement construction may be conducted to change a steep curve to a moderate curve. If such a change is not reflected in the map data, a comfort driving operation of the driver may be impaired, for instance, by causing the vehicle to unnecessarily decelerate although there is no curve.
The same situation may arise even when no road construction has been conducted. For example, when a curve of a road ahead of the vehicle is detected by using a dedicated map data analysis program, an erroneous curve detection may occur. In such an instance, too, a comfort driving operation of the driver may be impaired, for instance, by causing the vehicle to unnecessarily decelerate at a place without a curve. Further, as far as the same map data is analyzed, it is highly likely that an erroneous curve detection may occur again when the vehicle passes through the same place. Consequently, a comfort driving operation may be impaired, for instance, by causing the vehicle to unnecessarily decelerate each time it passes through the same place.
Under the above circumstances, a technology proposed, for instance, in Patent Literature 1 determines whether the vehicle is traveling along a curve detected from map data. If the vehicle diverts from the curve detected from the map data, the proposed technology suppresses control that is exercised to assist a driver of the vehicle in passing through the curve when the vehicle will later pass through the curve.
Patent Literature 1: JP4860391B corresponding to US2008/0024266A1